Preparation method of heat-resistant methyl phenyl silicone oil

Abstract

The invention provides the preparation method of the heat-resistant methyl phenyl silicone oil, the process is simple and convenient, the arrangement of methyl phenyl structural units is uniform, and the content of ethyoxyl is low. The preparation method comprises the following steps: carrying out partial monomer modification on methylphenylsiloxane hydrolysate by adding a metal compound to form a stable Si-O-M bond (M is a metal component), carrying out two-stage equilibrium reaction on methylphenylsiloxane condensate and hexamethyldisiloxane, supplementing an alkaline catalyst, deionized water and a polar solvent in the second-stage reaction, and carrying out polymerization reaction to obtain the high-molecular-weight polydimethylsiloxane. The hydrolysis of residual alkoxy and the condensation of hydroxyl are promoted, the arrangement of a methyl phenyl structure unit and the precise control of an impurity end-capping group are synergistically realized, and the thermal stability of the methyl phenyl silicone oil is greatly improved.

Description

The application belongs to the technical field of silicone oil preparation, and particularly relates to a preparation method of heat-resistant methylphenyl silicone oil. As a kind of excellent performance silicone material, methylphenyl silicone oil plays an important role in high-end fields such as aerospace, electronics and nuclear industry. With the progress of science and technology, these application fields have put forward more stringent requirements for the heat resistance of methylphenyl silicone oil. Its heat resistance is closely related to the molecular structure, mainly restricted by two key factors: one is the arrangement order of methylphenyl structural units in the main chain; the other is the content of impurity end-capping groups such as alkoxy groups remaining at the end of the molecular chain.

[0003] Firstly, the arrangement order of methylphenyl structural units in the polysiloxane molecular chain has an important influence on the heat resistance of the silicone oil. The more uniform the distribution of methylphenyl structural units in the polysiloxane molecular main chain, the better the heat resistance. Chinese patent document CN115819773B discloses a preparation method of high-temperature-resistant benzyl silicone oil with narrow molecular weight distribution. First, 1,3,5-trimethyl-1,3,5-triphenylcyclotrisiloxane is added dropwise into a n-butyllithium solution, then hexamethylcyclotrisiloxane is added dropwise, and finally trimethylchlorosilane is used for end-capping to obtain a block type benzyl silicone oil. The benzyl silicone oil has good high-temperature resistance, but since the methylphenyl structural units are not uniformly distributed in the molecular chain, its heat resistance still needs to be improved.

[0004] Furthermore, during the synthesis of methylphenyl silicone oil, impurity end-capping groups such as methoxy and ethoxy also have an important influence on its heat resistance. The residual alkoxy groups in the silicone oil will undergo hydrolysis and condensation reaction under high temperature and water conditions, and intermolecular crosslinking reaction occurs, resulting in viscosity increase or gelation. Chinese patent document CN109776801B discloses a preparation method of phenyl silicone oil. Diphenylalkoxysilane and dimethylalkoxysilane are used as raw materials to synthesize phenyl silicone oil. A hydrolysis promoter is used in the synthesis process, which can effectively reduce the content of methoxy groups and thus improve the thermal stability of the product, but it is still quite difficult to reduce the content of ethoxy groups. Since ethoxy group has one more methylene group than methoxy group, the strong electron-donating effect of ethyl group increases the electron cloud density of oxygen atom, reduces the electrophilicity of silicon atom, and the steric hindrance of ethoxy group is larger, so it is more difficult to hydrolyze than methoxy group.

[0005] ​​In addition, in order to improve the heat resistance of silicone oil, the introduction of metal compounds such as Ce and Zr into silicone oil plays a key role. Chinese patent document CN110294847B discloses a method for improving the thermal stability of low viscosity silicone oil in an oxygen environment. The low viscosity silicone oil is heat treated with metal oxides or mixtures thereof treated by vacuum drying. The obtained silicone oil has low decomposition rate in air and good thermal stability. However, due to the poor compatibility of solid-liquid two phases, the two phases are not easy to combine, and subsequent separation of solid-liquid two phases is required, which limits the modification effect to a certain extent. SUMMARY In order to solve the problems of the preparation method of methylphenyl silicone oil in the prior art, the present application provides a preparation method of heat-resistant methylphenyl silicone oil with simple modification method, uniform arrangement of methylphenyl structural units and low ethoxy content.

[0007] The present application is realized by the following technical solutions: A preparation method of heat-resistant methylphenyl silicone oil, comprising the following steps: S1, partial monomer modification: adding methylphenyl siloxane hydrolysate into a reaction container, adding metal compounds, and introducing nitrogen protection, so that the metal compounds react with the methylphenyl siloxane hydrolysate to obtain methylphenyl siloxane hydrolysate modified by metal; S2, condensation reaction: adding an alkaline catalyst to the methylphenyl siloxane hydrolysate of step S1, so that the alkaline catalyst and the methylphenyl siloxane hydrolysate perform condensation reaction to obtain methylphenyl siloxane condensate; S3, equilibrium reaction: adding hexamethyldisiloxane to the methylphenyl siloxane condensate of step S2, so that the hexamethyldisiloxane and the methylphenyl siloxane condensate perform first stage reaction, additional alkaline catalyst, deionized water and polar solvent are added, and second stage reaction is performed. After the second stage reaction is completed, condensation is performed by negative pressure, and then the solvent is removed by heating and negative pressure to obtain an equilibrium product; S4, medium breaking: heating the equilibrium product of step S3 to break the medium and obtain a medium breaking product; S5, low removal: transferring the medium breaking product of step S4 to a low removal container, introducing nitrogen, so that the medium breaking product is removed, and obtaining heat-resistant methylphenyl silicone oil.

[0008] The structure of the methylphenyl siloxane hydrolysate in step S1 is:

[0009] In the formula, n=1-5; the residual amount of alkoxy is about 1wt%, and the alkoxy is methoxy and ethoxy.

[0010] The present application is based on the following reaction principle:

[0011] Firstly, the metal compound is used to partially modify the methyl phenyl siloxane hydrolysate. The methyl phenyl siloxane hydrolysate is modified by the metal compound at a certain temperature to form a stable Si-O-M bond (M is the metal component in the compound), which can effectively protect the polysiloxane chain from oxidation and damage at high temperature, thereby improving the heat resistance of the methyl phenyl silicone oil. After modification, the methyl phenyl siloxane hydrolysate needs to be cooled and then subjected to condensation reaction, otherwise the temperature of the reactants is too high, which will cause the catalyst added subsequently to lose activity.

[0012] Secondly, the methyl phenyl siloxane hydrolysate is used as a structural unit to carry out chain extension under the action of an alkaline catalyst, which can ensure uniform distribution of methyl phenyl on the polysiloxane molecular chain and form a more stable structure to enhance the thermal stability of the molecular chain.

[0013] Thirdly, hexamethyldisiloxane is used as an end-capping agent to carry out the first stage reaction with the methyl phenyl siloxane condensate, complete the end-capping of the chain and the preliminary equilibrium reaction, and then add an alkaline catalyst, deionized water and a polar solvent in the second stage reaction to carry out hydrolysis reaction under normal pressure. The introduction of the polar solvent can further dissolve the originally two-phase silicone oil and water, thereby increasing the contact area of water and silicone oil and the contact probability of water molecules and alkoxy groups (especially ethoxy groups), promoting the hydrolysis of residual alkoxy groups in the alkaline environment, and then carrying out negative condensation to effectively remove the alkoxy and hydroxy impurity groups in the methyl phenyl silicone oil. Through the two-stage equilibrium reaction, the arrangement of the methyl phenyl structural unit and the precise control of the end-capping groups of impurities are realized, which greatly improves the thermal stability of the methyl phenyl silicone oil.

[0014] Preferably, the metal compound in step S1 is one of cerium iso-octoate, zirconium iso-octoate and manganese iso-octoate, and the amount of the metal compound is 0.5-3% of the weight of the methyl phenyl siloxane hydrolysate.

[0015] The present application uses iso-octoate metal compound as a modifier, which is in liquid state and has excellent organic compatibility, can be uniformly dissolved with the methyl phenyl siloxane hydrolysate, avoids the agglomeration or precipitation of metal particles, and does not need additional solvents. At the same time, it has a high thermal decomposition temperature and can maintain structural integrity during the reaction process to ensure that the metal component effectively participates in the modification of the monomer. In addition, at a low dosage, the heat resistance of the methyl phenyl silicone oil can be significantly improved.

[0016] More preferably, the metal compound is cerium iso-octoate, and the amount is 1-2% of the weight of the methyl phenyl siloxane hydrolysate.

[0017] Preferably, the reaction conditions in step S1 are temperature: 120-170℃, reaction time: 2-6h. More preferably, the temperature is 150℃, and the reaction time is 4h.

[0018] Preferably, the basic catalyst in steps S2 and S3 is one of (CH3)4NOH, NaOH, and KOH, and the amount of the basic catalyst in step S2 is 500-1000ppm.

[0019] The present application uses a basic catalyst to promote the condensation reaction of silicon hydroxyl groups in the modified methyl phenyl siloxane hydrolysis material in step S2, to generate a methyl phenyl siloxane condensate. In step S3, the methyl phenyl siloxane condensate is promoted to undergo an equilibrium reaction with the end-capping agent hexamethyldisiloxane, and by adding a basic catalyst in the second stage reaction, the residual alkoxy groups are promoted to undergo hydrolysis and condensation, further removing methoxy and ethoxy groups, thereby improving the stability of the methyl phenyl silicone oil. At the same time, the added catalyst can accelerate the dynamic rearrangement of the siloxane chain, promote the reaction system to quickly reach a new equilibrium state, and ensure that the end groups are fully capped, ensuring the integrity and structural stability of the silicone oil molecular chain.

[0020] More preferably, the basic catalyst is (CH3)4NOH, and the amount is 800ppm.

[0021] Among them, tetramethylammonium hydroxide has high reactivity, and as the reaction temperature increases, tetramethylammonium hydroxide can be decomposed into a gas without being left in the product, improving the purity and quality of the product.

[0022] Preferably, the condensation reaction conditions in step S2 are a reaction temperature of 70-120℃, a vacuum degree of -0.05 to -0.1MPa, and a reaction time of 0.5-5h; after the condensation reaction is completed, nitrogen is used to relieve the pressure to restore normal pressure, which can avoid the oxidation of the product when it is restored to normal pressure, thereby ensuring the purity and quality of the product.

[0023] More preferably, the reaction temperature is 80-100℃, the vacuum degree is -0.09MPa, and the condensation time is 1-2h.

[0024] Preferably, the amount of the basic catalyst added in step S3 is 200-1000ppm of the total amount of methyl phenyl siloxane condensate and hexamethyldisiloxane.

[0025] More preferably, the amount of the basic catalyst added is 400ppm.

[0026] Preferably, the amount of deionized water used in step S3 is 1000-2000ppm of the total amount of methyl phenyl siloxane condensate and hexamethyldisiloxane.

[0027] More preferably, the amount of deionized water is 1200 ppm.

[0028] Preferably, the polar solvent in step S3 is one of N,N-dimethylformamide, n-butanol, and isobutyl alcohol, and the amount of the polar solvent is 5-15% of the total amount of methylphenylsiloxane condensate and hexamethyldisiloxane.

[0029] More preferably, the polar solvent is N,N-dimethylformamide, and the amount is 10%.

[0030] The present application uses a polar solvent as a medium to further dissolve the originally immiscible silicone oil and water, thereby increasing the contact area of water and silicone oil, and further increasing the contact probability of water molecules and alkoxy groups (especially ethoxy groups), promoting the hydrolysis of residual alkoxy groups in an alkaline environment, and then performing negative condensation to effectively remove alkoxy and hydroxyl impurity groups in methylphenylsilicone oil.

[0031] Preferably, the reaction conditions in the first stage of step S3 are a reaction temperature of 70-120°C and a reaction time of 2-10h. More preferably, the reaction temperature is 80-100°C, and the reaction time is 4h.

[0032] Preferably, the reaction conditions in the second stage of step S3 are a reaction temperature of 70-120°C and a reaction time of 1-5h. More preferably, the reaction temperature is 90-100°C, and the reaction time is 2-3h.

[0033] Preferably, the condensation conditions in step S3 are a temperature of 80-110°C, a time of 1-2h, and a vacuum degree of -0.05 to -0.1 MPa. More preferably, the temperature is 95-100°C, the time is 1h, and the vacuum degree is -0.085 to -0.095 MPa.

[0034] Preferably, when the solvent is removed in step S3, the temperature is 120-130°C, and the vacuum degree is -0.05 to -0.1 MPa. More preferably, the temperature is 130°C, and the vacuum degree is -0.09 MPa.

[0035] Preferably, the breaking medium conditions in step S4 are a breaking medium temperature of 150-180°C and a breaking medium time of 1-3h. More preferably, the breaking medium temperature is 160°C, and the breaking medium time is 2h.

[0036] Preferably, the low-temperature removal conditions in step S5 are a low-temperature removal temperature of 250-350°C, a vacuum degree of -0.1 MPa, and a low-temperature removal time of 2-8h. More preferably, the low-temperature removal temperature is 320-330°C, and the low-temperature removal time is 4-6h.

[0037] The beneficial effects of the present application are as follows: The application adopts metal compounds to perform partial monomer thermal modification on methyl phenyl siloxane hydrolysate, and the partial methyl phenyl siloxane hydrolysate forms a stable Si-O-M bond (M is a metal component in the compound) after being modified by the metal compounds under certain temperature conditions, which can effectively protect the polysiloxane chain from being oxidized and damaged at high temperatures, thereby improving the heat resistance of the methyl phenyl silicone oil. Second, the methyl phenyl siloxane hydrolysate is used as a structural unit to perform chain extension under the action of an alkaline catalyst, which can ensure uniform distribution of methyl phenyl on the polysiloxane molecular chain and form a more stable structure to enhance the thermal stability of the molecular chain. Third, hexamethyldisiloxane is used as an end-capping agent to perform a first stage reaction with the methyl phenyl siloxane condensate, complete end capping and preliminary equilibrium reaction, and then add an alkaline catalyst, deionized water and a polar solvent in a second stage reaction to perform a hydrolysis reaction under normal pressure. The polar solvent makes the originally two-phase silicone oil and water further miscible, thereby increasing the contact area of water and silicone oil, and further increasing the contact probability of water molecules and alkoxy groups (especially ethoxy groups), promoting the hydrolysis of residual alkoxy groups in an alkaline environment, and then performing a negative condensation to effectively remove alkoxy and hydroxyl impurity groups in the methyl phenyl silicone oil. Through two-stage equilibrium reaction, the arrangement of methyl phenyl structural units and the precise control of impurity end-capping groups are realized, and the thermal stability of the methyl phenyl silicone oil is greatly improved. DETAILED DESCRIPTION The specific technical solutions of the application are described below in combination with Examples 1-3: Example 1 A preparation method of a heat-resistant methyl phenyl silicone oil, comprising the following steps: S1, partial monomer modification: 300 g of methyl phenyl siloxane hydrolysate is added to a reaction flask, 3 g of cerium isooctoate is added, and nitrogen is introduced for protection, so that the cerium isooctoate reacts with the methyl phenyl siloxane hydrolysate at 150℃ for 4 h to obtain a methyl phenyl siloxane hydrolysate modified by a metal; S2, condensation reaction: the methyl phenyl siloxane hydrolysate in step S1 is cooled to 100℃, and 0.24 g of (CH3)4NOH is added, so that the (CH3)4NOH and the modified methyl phenyl siloxane hydrolysate are subjected to a condensation reaction at 100℃ and -0.09 MPa for 2 h to obtain a methyl phenyl siloxane condensate; S3, equilibrium reaction: 22.39 g of hexamethyldisiloxane was added to the methylphenylsiloxane condensate described in step S2, so that the hexamethyldisiloxane and the methylphenylsiloxane condensate were subjected to a first stage reaction at 100°C under normal pressure for 4 h, 0.13 g of (CH3)4NOH, 0.36 g of deionized water and 30.4 g of N,N-dimethylformamide were added, and a second stage reaction was carried out at 95°C under stirring for 3 h, after the second stage reaction was completed, condensation was carried out at 100°C under -0.09 MPa for 1 h, and then the temperature was raised to 130°C, and the solvent was removed under -0.08 MPa to obtain an equilibrium product; S4, medium breaking: the pressure was restored to normal pressure by nitrogen pressure relief, and the equilibrium product described in step S3 was heated to 160°C to break the medium for 2 h to obtain a medium breaking product; S5, low boiling point removal: the medium breaking product described in step S4 was transferred to a low boiling point removal flask, a small amount of nitrogen was introduced, and the medium breaking product was subjected to low boiling point removal at 320°C under -0.1 MPa for 4 h to obtain 288.4 g of heat-resistant methylphenylsilicone oil.

[0039] Example 2 A method for preparing heat-resistant methylphenylsilicone oil, comprising the following steps: S1, partial monomer modification: 300 g of methylphenylsiloxane hydrolysate was added to a reaction flask, 3 g of cerium isooctanoate was added, and nitrogen was introduced for protection, so that the cerium isooctanoate reacted with the methylphenylsiloxane hydrolysate at 150°C for 4 h to obtain a methylphenylsiloxane hydrolysis material partially modified by a metal; S2, condensation reaction: the methylphenylsiloxane hydrolysis material described in step S1 was cooled to 100°C, and 0.24 g of (CH3)4NOH was added, so that the (CH3)4NOH and the modified methylphenylsiloxane hydrolysis material were subjected to a condensation reaction at 100°C under -0.09 MPa for 2 h to obtain a methylphenylsiloxane condensate; S3, equilibrium reaction: 22.39 g of hexamethyldisiloxane was added to the methylphenylsiloxane condensate described in step S2, so that the hexamethyldisiloxane and the methylphenylsiloxane condensate were subjected to a first stage reaction at 100°C under normal pressure for 4 h, 0.12 g of (CH3)4NOH, 0.36 g of deionized water and 30.5 g of N,N-dimethylformamide were added, and a second stage reaction was carried out at 95°C under stirring for 3 h, after the second stage reaction was completed, condensation was carried out at 100°C under -0.09 MPa for 1 h, and then the temperature was raised to 130°C, and the solvent was removed under -0.08 MPa to obtain an equilibrium product; S4, medium breaking: the pressure was restored to normal pressure by nitrogen pressure relief, and the equilibrium product described in step S3 was heated to 160°C to break the medium for 2 h to obtain a medium breaking product; S5, low removal: the broken medium product of step S4 is transferred to a low removal flask, a small amount of nitrogen is introduced, and the broken medium product is subjected to low boiling point removal at 320℃ and -0.1MPa for 4h to obtain 287.9g of heat-resistant methyl phenyl silicone oil.

[0040] Example 3 A method for preparing heat-resistant methyl phenyl silicone oil, comprising the following steps: S1, partial monomer modification: 300g of methyl phenyl siloxane hydrolysate is added to a reaction flask, 3g of cerium isooctanoate is added, and nitrogen is introduced for protection, so that the cerium isooctanoate reacts with the methyl phenyl siloxane hydrolysate at 150℃ for 4h to obtain a methyl phenyl siloxane hydrolysate modified by a metal; S2, condensation reaction: the methyl phenyl siloxane hydrolysate of step S1 is cooled to 100℃, and 0.24g of (CH3)4NOH is added, so that (CH3)4NOH and the modified methyl phenyl siloxane hydrolysate are subjected to condensation reaction at 100℃ and -0.09MPa for 2h to obtain a methyl phenyl siloxane condensate; S3, equilibrium reaction: 47.99g of hexamethyldisiloxane is added to the methyl phenyl siloxane condensate of step S2, so that the hexamethyldisiloxane and the methyl phenyl siloxane condensate are subjected to first stage reaction at 100℃ and normal pressure for 4h, 0.14g of (CH3)4NOH, 0.37g of deionized water and 30.5g of N,N-dimethylformamide are added, and second stage reaction is carried out at 95℃ for 3h while stirring, and then condensation is carried out at 100℃ and -0.09MPa for 1h, and then the temperature is raised to 130℃, and the solvent is removed at -0.08MPa to obtain an equilibrium product; S4, medium breaking: the pressure is released to normal pressure by nitrogen, the equilibrium product of step S3 is heated to 160℃, and medium breaking is carried out for 2h to obtain a broken medium product; S5, low removal: the broken medium product of step S4 is transferred to a low removal flask, a small amount of nitrogen is introduced, and the broken medium product is subjected to low boiling point removal at 320℃ and -0.1MPa for 4h to obtain 285.7g of heat-resistant methyl phenyl silicone oil.

[0041] Comparative Example 1 A method for preparing methyl phenyl silicone oil, comprising the following steps: S1, condensation reaction: 300g of methyl phenyl siloxane hydrolysate is added to a reaction flask, 0.24g of (CH3)4NOH is added, so that (CH3)4NOH and the methyl phenyl siloxane hydrolysate are subjected to condensation reaction at 100℃ and -0.09MPa for 2h to obtain a methyl phenyl siloxane condensate; S2, equilibrium reaction: 22.39 g of hexamethyldisiloxane was added to the methylphenylsiloxane condensate described in step S2, so that the hexamethyldisiloxane and the methylphenylsiloxane condensate were subjected to a first stage reaction at 100°C under normal pressure for 4 h, 0.13 g of (CH3)4NOH, 0.36 g of deionized water and 30.4 g of N,N-dimethylformamide were added, and a second stage reaction was carried out at 95°C for 3 h while stirring, and after the second stage reaction was completed, condensation was carried out at 100°C under -0.09 MPa for 1 h, and then by increasing the temperature to 130°C, the solvent was removed under -0.08 MPa to obtain an equilibrium product; S3, medium breaking: by nitrogen pressure relief to restore to normal pressure, by warming up to 160°C for 2 h, the equilibrium product described in step S2 was subjected to medium breaking to obtain a medium breaking product; S4, low boiling point removal: the medium breaking product described in step S3 was transferred to a low boiling point removal flask, a small amount of nitrogen was introduced, and the medium breaking product was subjected to low boiling point removal at 320°C under -0.1 MPa for 4 h to obtain 286.4 g of heat-resistant methylphenylsilicone oil.

[0042] Comparative Example 2 A method for preparing a methylphenylsilicone oil, comprising the following steps: S1, partial monomer modification: 300 g of methylphenylsiloxane hydrolysate was added to a reaction flask, 3 g of cerium isooctanoate was added, and nitrogen was introduced for protection, so that the cerium isooctanoate reacted with the methylphenylsiloxane hydrolysate at 150°C for 4 h to obtain a methylphenylsiloxane hydrolysate modified by a metal; S2, condensation reaction: the methylphenylsiloxane hydrolysate described in step S1 was cooled to 100°C, and 0.24 g of (CH3)4NOH was added, so that the (CH3)4NOH and the modified methylphenylsiloxane hydrolysate were subjected to a condensation reaction at 100°C under -0.09 MPa for 2 h to obtain a methylphenylsiloxane condensate; S3, equilibrium reaction: 22.39 g of hexamethyldisiloxane was added to the methylphenylsiloxane condensate described in step S2, so that the hexamethyldisiloxane and the methylphenylsiloxane condensate were subjected to a first stage reaction at 100°C under normal pressure for 4 h to obtain an equilibrium product; S4, medium breaking: by nitrogen pressure relief to restore to normal pressure, by warming up to 160°C for 2 h, the equilibrium product described in step S3 was subjected to medium breaking to obtain a medium breaking product; S5, low boiling point removal: the medium breaking product described in step S4 was transferred to a low boiling point removal flask, a small amount of nitrogen was introduced, and the medium breaking product was subjected to low boiling point removal at 320°C under -0.1 MPa for 4 h to obtain 288.4 g of heat-resistant methylphenylsilicone oil.

[0043] Comparative Example 3 A preparation method of methylphenyl silicone oil, comprising the following steps: S1, condensation reaction: 300 g of methylphenyl siloxane hydrolysate is added to a reaction flask, 0.24 g of (CH3)4NOH is added, and the (CH3)4NOH and the methylphenyl siloxane hydrolysate are subjected to a condensation reaction at 100°C and -0.09 MPa for 2 h to obtain a methylphenyl siloxane condensate; S2, equilibrium reaction: 22.39 g of hexamethyldisiloxane is added to the methylphenyl siloxane condensate described in step S2, and the hexamethyldisiloxane and the methylphenyl siloxane condensate are subjected to a first stage reaction at 100°C and normal pressure for 4 h to obtain an equilibrium product; S3, medium breaking: the medium is broken by recovering to normal pressure through nitrogen pressure relief, and the equilibrium product described in step S2 is heated to 160°C to break the medium for 2 h to obtain a medium breaking product; S4, low boiling point removal: the medium breaking product described in step S3 is transferred to a low boiling point removal flask, a small amount of nitrogen is introduced, and the medium breaking product is subjected to low boiling point removal at 320°C and -0.1 MPa for 4 h to obtain 282.3 g of heat-resistant methylphenyl silicone oil.

[0044] The performance tests of the above examples 1-3 and comparative examples 1-3 are carried out, and the test conditions are as follows, and the test data are shown in Table 1.

[0045] Thermal gelation test: 40 g of the sample is placed in a 100 mL beaker (diameter 52 mm, height 76 mm), and the sample is baked in a high-temperature air oven at 280°C, and the state of the sample is observed every 5 h to see if it has gelled. And, the weight of the gelled sample is tested to calculate the volatile components.

[0046] Table 1 methylphenyl silicone oil data of examples 1-3 and comparative examples 1-3

[0047] Note: “D” means detected, and “ND” means not detected.

[0048] As shown in Table 1, compared with comparative examples 1-3, the methylphenyl silicone oil of examples 1-3 has uniform methylphenyl structural unit arrangement, less methoxy and ethoxy impurity end-capping groups, and excellent heat resistance, and can remain un-gelled in a high-temperature air environment at 280°C for 250 h, and the volatile components are within 10%.

[0049] Specifically, the methylphenylsilicone hydrolyzate in Examples 1 and 2 was partially thermally modified by different metal compounds, and both of the methylphenylsilicone oils had excellent heat resistance. This indicates that the use of metal compounds for modification has universal applicability in improving the heat resistance of methylphenylsilicone oils. Compared with Examples 1 and 2, the heat resistance of the methylphenylsilicone oil in Example 3 was slightly worse because it had a lower viscosity, a smaller molecular weight, and a shorter molecular chain.

[0050] Compared with Examples 1-3, the heat resistance of Comparative Examples 1-3 was significantly worse, and all gelled within 180 h in a 280℃ high-temperature air blowing environment, and the volatile components were all greater than 10%.

[0051] Specifically, the heat resistance of the methylphenylsilicone oil in Comparative Example 1, which was not partially monomer modified by metal compounds, decreased significantly. Although monomer modification was used, the heat resistance of the methylphenylsilicone oil in Comparative Example 2, which did not go through the hydrolysis and condensation processes in the balanced reaction process, also decreased significantly, and residual methoxy and ethoxy groups could be detected. Comparative Example 3, which did not add metal compounds and did not use the hydrolysis and condensation processes, could also detect residual methoxy and ethoxy groups, and had the worst heat resistance.

[0052] The above only uses examples to further illustrate the technical content of the present application, so that the reader can more easily understand, but does not represent that the embodiments of the present application are limited to this, any technical extension or re-creation made according to the present application is protected by the present application. The scope of protection of the present application is subject to the claims.

Claims

1. A method for preparing a heat-resistant methylphenyl silicone oil, characterized in that: Includes the following steps: S1. Partial Monomer Modification: Methylphenylsiloxane hydrolysate is added to a reaction vessel, a metal compound is added, and nitrogen gas is introduced for protection, so that the metal compound reacts with the methylphenylsiloxane hydrolysate to obtain partially metal-modified methylphenylsiloxane hydrolysate. S2, Condensation reaction: An alkaline catalyst is added to the methylphenylsiloxane hydrolysate from step S1, so that the alkaline catalyst and the methylphenylsiloxane hydrolysate undergo a condensation reaction to obtain a methylphenylsiloxane condensate. S3. Equilibrium reaction: Hexamethyldisiloxane is added to the methylphenylsiloxane condensate described in step S2, so that the hexamethyldisiloxane and the methylphenylsiloxane condensate undergo a first-stage reaction. An alkaline catalyst, deionized water and a polar solvent are added to carry out a second-stage reaction. After the second-stage reaction is completed, condensation is carried out under negative pressure, and then the solvent is removed by heating and negative pressure to obtain the equilibrium product. S4, Degradation: Degradation is carried out by heating the equilibrium product described in step S3 to obtain the degraded product; S5. Degradation: The degrading product obtained in step S4 is transferred to a degradation container, and nitrogen gas is introduced to degrade the degrading product, thereby obtaining heat-resistant methylphenyl silicone oil.

2. The method for preparing the heat-resistant methylphenyl silicone oil according to claim 1, characterized in that: The structural formula of the methylphenylsiloxane hydrolysate in step S1 is: Wherein, n=1~5; alkoxy residue ≈1wt%, the alkoxy group is methoxy and ethoxy.

3. The method for preparing the heat-resistant methylphenyl silicone oil according to claim 1, characterized in that: The metal compound in step S1 is one of cerium isooctanoate, zirconium isooctanoate, and manganese isooctanoate, and the amount of the metal compound used is 0.5 to 3% of the weight of the methylphenylsiloxane hydrolysate.

4. The method for preparing the heat-resistant methylphenyl silicone oil according to claim 1, characterized in that: The reaction conditions described in step S1 are: temperature: 120–170°C, reaction time: 2–6 h.

5. The method for preparing the heat-resistant methylphenyl silicone oil according to claim 1, characterized in that: The alkaline catalyst used in steps S2 and S3 is one of (CH3)4NOH, NaOH, and KOH; the amount of alkaline catalyst used in step S2 is 500-1000 ppm.

6. The method for preparing the heat-resistant methylphenyl silicone oil according to claim 1, characterized in that: The condensation reaction conditions in step S2 are: reaction temperature of 70-120℃, vacuum degree of -0.05--0.1MPa, and reaction time of 0.5-5h; after the condensation reaction is completed, nitrogen gas is used to depressurize and restore atmospheric pressure.

7. The method for preparing the heat-resistant methylphenyl silicone oil according to claim 1, characterized in that: The amount of alkaline catalyst added in step S3 is 200 to 1000 ppm of the total amount of methylphenylsiloxane condensate and hexamethyldisiloxane. The amount of deionized water used in step S3 is 1000-2000 ppm of the total input of methylphenylsiloxane condensate and hexamethyldisiloxane; The polar solvent in step S3 is one of N,N-dimethylformamide, n-butanol, and isobutanol, and the amount of the polar solvent used is 5-15% of the total amount of methylphenylsiloxane condensate and hexamethyldisiloxane.

8. The method for preparing the heat-resistant methylphenyl silicone oil according to claim 1, characterized in that: Step S3: The reaction conditions for the first stage are: reaction temperature: 70-120℃, reaction time: 2-10h; Step S3: The reaction conditions for the second stage are: reaction temperature: 70-120℃, reaction time: 1-5h; The condensation conditions described in step S3 are: temperature: 80~110℃, time: 1~2h, and vacuum degree: -0.05~-0.1MPa; During solvent removal in step S3, the temperature is 120-130℃ and the vacuum degree is -0.05--0.1MPa.

9. The method for preparing the heat-resistant methylphenyl silicone oil according to claim 1, characterized in that: The decomposition conditions described in step S4 are: decomposition temperature: 150-180℃, decomposition time: 1-3h.

10. The method for preparing the heat-resistant methylphenyl silicone oil according to claim 1, characterized in that: The de-lowering conditions described in step S5 are: de-lowering temperature: 250~350℃, vacuum degree: -0.1MPa, and de-lowering time: 2~8h.

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